A5004053762- Liquid Crystal Research Advancements
- Photochromic and Fluorescence Chemistry
- Luminescence and Fluorescent Materials
- Synthesis and Properties of Aromatic Compounds
- Organic Light-Emitting Diodes Research
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Photochemistry and Electron Transfer Studies
- Molecular spectroscopy and chirality
- Click Chemistry and Applications
- Monoclonal and Polyclonal Antibodies Research
- Chemistry Education and Research
- Molecular Sensors and Ion Detection
- Synthesis and Biological Evaluation
- Vanadium and Halogenation Chemistry
- Chemical Synthesis and Reactions
- Crystallography and molecular interactions
- Carbon dioxide utilization in catalysis
- Chemical Synthesis and Analysis
- Ionic liquids properties and applications
- Synthesis and properties of polymers
- Various Chemistry Research Topics
- Synthesis of heterocyclic compounds
- Porphyrin and Phthalocyanine Chemistry
- Natural Compound Pharmacology Studies
Universidade Federal da Paraíba
2014-2025
Universidade Federal de Santa Catarina
2003-2010
Georgetown University
2009-2010
University of Washington
2010
A general synthetic strategy, based on a convergent approach, allowed us to prepare series of luminescent unsymmetrical bent‐core compounds (2,5‐(disubstituted)‐1,3,4‐oxadiazole derivatives), via the Sonogashira crosscoupling reaction, all possessing similar hockey stick shape. Their mesophases were characterized using polarizing optical microscopy and differential scanning calorimetry. The observed LC phases possess classical textures calamitic liquid crystals. Fluorescence in solution for...
The synthesis and structural, thermal, optical theoretical characterization of new tris[1,2,4]triazolo[1,3,5]triazines were performed to support their application as liquid crystals advanced materials.
Five discotic molecules comprising a tris[1,2,4]triazolo[1,3,5] triazine core were designed and synthesized to obtain luminescent charge-transporting columnar liquid crystalline materials. With the exception of one compound containing terminal hydroxyl groups all compounds presented wide thermal range stable phase, characterized by differential scanning calorimetry, polarized optical microscopy, X-ray diffraction (XRD) techniques. The phase formation appeared be associated some extent with...
Two series of highly π-conjugated calamitic liquid crystals containing a sulphur-based heterocyclic core, 1,3,4-thiadiazole or 1,3-thiazole ring, were synthesised and characterised. The part the heterocycle was linked to π-extended mesogenic unit (phenyl, biphenyl, naphthyl phenylbenzoate) through carbon–carbon triple bond by Sonogashira's cross coupling, in order exhibit crystalline luminescent properties. These compounds exhibited behaviour special SmC phase presented all compounds,...
Abstract Symmetric and asymmetric bent‐shape LCs were synthesized, having the emissive core 1,3,4‐oxadiazole with C≡C bonds as connecting groups, terminal nitro lateral substituents. Thermal behaviour was determined using optical microscopy differential scanning calorimetry. Lowering of transition temperatures and/or induction new smectic phases in symmetric compounds observed on introduction polar compared unsubstituted compounds. The LC possess classical textures calamitic liquid crystals...
The synthesis, and liquid crystalline photophysical properties of luminescent compounds based on 1,3‐bis[5‐(4‐alkoxyphenyl)‐1,3,4‐oxadiazole‐2‐yl]benzene (two‐fold symmetry) I 1,3,5‐tris[5‐(4‐alkoxyphenyl)‐1,3,4‐oxadiazole‐2‐yl]benzene II (three‐fold are described. mesophases were characterized using polarizing optical microscopy differential scanning calorimetry. In addition, all showed blue fluorescence with emission maxima between 366 382 nm, good quantum yields photoluminescence (ΦPL = 45%).
Thermal and optical behaviours of a series highly π‐conjugated hockey stick‐shaped non‐symmetrical 1,2,4‐oxadiazoles, with liquid crystalline properties, have been studied. All them presented phases, in particular smectic nematic phases typical calamitic compounds. Although these substances are thermally less stable than their 1,3,4‐oxadiazole isomers, they showed better behaviour lower melting points. UV–visible spectra compounds 1a–1f solution displayed similar absorption patterns maxima...
A series of highly π-conjugated nonsymmetrical liquid crystals, based on the core 3,5-(disubstituted)-1,2,4-oxadiazole with a shape similar to hockey stick, were successfully synthesized by convergent Sonogashira coupling reaction between building blocks aryl iodides and corresponding terminal arylacetylenes, using 3-[4-(decyloxy)phenyl]-5-(haloaryl)-1,2,4-oxadiazoles or decyl 4-iodobenzoate (10) arylacetylenes. This versatile synthetic route yielded luminescent mesogens smectic nematic...
Regioselective synthesis of [1,2,3]‐triazoles based on the 'click‐reaction', involving Cu(I)‐catalysed 1,3‐dipolar cycloaddition aryl azide to terminal arylacetylenes, was successfully employed in preparation two series non‐linear mesogens, 1,4‐diaryl‐[1,2,3]‐triazole (Ia–e) and with Schiff's base units (IIa–c). Their mesophases were characterized by polarizing optical microscopy differential scanning calorimetry. All final compounds exhibited preferentially SmC phase. In addition, I showed...
Six room temperature ionic liquids (RTILs) comprised of a tetraalkylphosphonium cation (tridecylmethyphosphonium or trihexyltetradecylphosphonium) and trihalide anion (Br(3)(-), BrCl(2)(-), ClBr(2)(-)) have been prepared characterized. Their ability to effect halogenation reactions with variety substrates has explored. In general, alkenes proceed high yields stereo- regioselectivities, whether performed in the absence presence solvent (chloroform). Reactions an alkyne electrophilic...
Abstract New nonlinear compounds containing 1,4‐diaryl‐[1,2,3]‐triazole were prepared using a straightforward and efficient method for the regioselective synthesis of [1,2,3]‐triazoles. The methodology consists Cu(I)‐catalyzed 1,3‐dipolar cycloaddition aryl azides to terminal arylacetylenes (click reaction). All exhibited liquid‐crystalline profile.
This Letter reports about the molecular alignment effects on absorbance and emission properties of a new compound based 2,1,3-benzothiadiazole guested in liquid crystals. The ordering is available for different chromophore concentrations. Despite increasing disorder above concentration 0.20%, samples always present high degree linear polarization fluorescence. A considerable amount polarized observed during isotropic phase (T > 58 °C), which attributed to light by aligned molecules before...
The incorporation of dyes in liquid crystal matrices has been exploited to produce enhanced displays, but it can also be used probe ordering crystals and assess intermolecular interactions dye aggregation. In this study, we investigated polarized absorption emission the luminescent 4,7-bis(2-(4-(decyloxy)phenyl)ethynyl)-[2,1,3]-benzothiadiazole (1A) 4,7-bis{2-[4-(4-decylpiperazin-1-yl)phenyl]ethynyl}-[2,1,3]-benzothiadiazole (5A) E7® crystal. electronic structures both 1A 5A were affected by...
Whereas perylene tetracarboxdiimides derived from amino-n-alkanes if at all only show monotropic (thermodynamically unstable) mesogenic self-assembly, the hexagonal columnar liquid crystalline state can be stabilized over a broad temperature range with doubly branched, racemic alkyl residues. An improved tendency to homeotropic surface orientation is observed, and of domains maintained upon cycling through room temperature.
Mono‐ and diglyoxylation of chrysene naphthalene leads to Perkin reactants that yield bismaleates, which efficiently photocyclize elongated phenacenetetracarboxylic esters. Their band gaps remain significantly larger than the value postulated for polyphenacene. The reaction with α‐branched amines gives corresponding imides, are stronger electron acceptors obtained [12]‐ [14]phenacenes longest [ n ]phenacenes have been synthesized date.
Polygala paniculata L. yielded the xanthones 1-hydroxy-5-methoxy-2,3-methylenedioxyxanthone (1) and 1,5-dihydroxy-2,3-dimethoxyxanthone (2), together with coumarin murragatin flavonol rutin. Their structures were established by chemical spectroscopic methods (EIMS, IR, 1H 13C NMR, NOE difference spectroscopy). By posterior analysis of an apolar crude extract using high resolution gas chromatography coupled to mass spectrometry (HRGC-MS) it was possible characterize two sterol (spinasterol...
The photocyclization of tetraethyl 1,4-phenylenebis(phenylmaleate) in the presence iodine and oxygen predominantly yields [5]helicene-5,6,9,10-tetracarboxylate, together with small amounts dibenz[a,h]anthracene-5,6,12,13-tetracarboxylate benzo[ghi]perylene-3,4,11,12-tetracarboxylate. helicene tetraester is planarized to benzoperylene by Scholl reaction AlCl3 followed reesterification partially hydrolyzed crude product. Subsequent treatment a branched alkylamine columnar liquid-crystalline...
Abstract The twofold glyoxylic Perkin reaction of perylene‐3,9‐diglyoxylic acid with thiophene‐diacetic followed by oxidative photocylization and α‐branched primary alkylamines yields columnar liquid‐crystalline diimides two sulfur atoms in the condensed arene system. A broad temperature range hexagonal mesophase is induced racemic doubly branched alkyl chains. HOMO LUMO energy levels these thiophene‐derived qualify them as electron donors respect to perylene diimides.
Delayed fluorescence (DF) by triplet-triplet annihilation (TTA) is observed in solutions of a benzoperylene-imidoester mesogen that shows hexagonal columnar mesophase at room temperature the neat state. A similar benzoperylene-imide with slightly smaller HOMO-LUMO gap, also liquid crystalline temperature, does not show DF solution, and mixtures two mesogens no solution either, because collisional quenching excited triplet states on imidoester imide. In contrast, TTA from imide but condensed...